This international, multicenter, real-world study, conducted on a large cohort of nearly 6000 patients with persistent pruritus and xerosis associated with a skin condition, systemic disease, or with persistent itch following successful treatment for scabies infestation, demonstrated that a 7-day regimen using the study product led to significant decreases in the severity of both xerosis and pruritus when used in real-life conditions, regardless of the underlying pathology. The study product was equally effective when used as a monotherapy and when used in combination with topical or systemic treatments. Use of the study product also appeared to reduce the duration of itch, reduced sleep disturbance, and lessened the impact of the skin symptoms on patient QoL. The product was well tolerated, and the vast majority of patients reported applying the product as directed by the physician.
Dry skin and associated pruritus result from impaired stratum corneum barrier function and disruption of epidermal homeostasis. Superficial dehydration of the stratum corneum induces a dry skin cycle that propagates xerosis by reducing the synthesis of the skin barrier lipids, ceramides, and disrupting the lipid bilayer [7]. Inflammatory responses and further damage to the stratum corneum then lead to dysfunctional keratinocyte proliferation and differentiation, and impaired epidermal desquamation [7]. Leaking of natural moisturizing factors (NMF) from the stratum corneum further enhances transepidermal water loss [7]. Understanding of the pathophysiology of pruritus has also recently progressed, with the identification of two signaling pathways involved in the transmission of itch: a histamine-dependent pathway and a histamine-independent pathway that appears to play the major role in chronic pruritus (reviewed by Song et al. [20]). Pruritic skin produces elevated levels of pruritogenic mediators—including tryptase, thromboxane A2, tumor necrosis factor-alpha (TNFα), leukotrienes, substance P, endothelin-1 (ET-1), interleukins (ILs), and nerve growth factor (NGF)—produced by dermal mast cells, keratinocytes, lymphocytes, and endothelial cells [20]. These pruritogens stimulate protease-activated receptor 2 (PAR2) and other receptors mediating histamine-independent itch, such as the Mas-related G protein-coupled receptors (MRGPRs), leading to activation of transient receptor potential cation channel subfamily V member 1 (TRPV1) and TRPA1, and transmission of the itch signal to the central nervous system by mechanically sensitive C-type fibers [20].
These advances in our understanding of the pathophysiology of xerosis and pruritus have led to the development of new emollients with specific activities targeting factors involved in the development of dry and itchy skin. The product investigated in our study was an emollient “plus” containing ADE-G1 as the active non-medicated substance. In vitro studies have shown that ADE-G1 displays several properties that are likely beneficial for the treatment of pruritus and xerosis, including immunomodulatory and anti-inflammatory activities that alter the expression of a range of inflammatory mediators [11]. Importantly, ADE-G1 also appears to have antipruritic activities, with in vitro studies showing that the extract inhibits PAR2 activation and T helper type (Th) 1, Th2, and Th17 cytokine production [11]. A prospective, placebo-controlled study using the cowhage–itch model confirmed the antipruritic properties of the ADE-G1-containing emollient and moreover demonstrated that the extract specifically inhibited the nonhistaminergic itch pathway [21]. Finally, the study product has already been shown to lead to significant decreases in xerosis severity (percentage of patients with mild xerosis increasing from 50% at the start of the study to 96.4% after 28 days of treatment) and pruritus (74.6% reduction in severity scores) in children with mild atopic dermatosis [13].
In this study, we demonstrated the effectiveness in a real-world setting of a 7-day regimen with the study product at reducing the severity of xerosis and pruritus by more than 50%. Moisturizers containing emollients, occlusive agents, and humectants are the mainstay of treatment for xerosis and pruritus. They may reduce the need for pharmacologic interventions and have a steroid-sparing effect in patients with some diseases, such as atopic dermatitis [22, 23]. Studies on a number of emollients, all generally containing similar active agents—e.g., petrolatum, paraffin, glycerin, and plant-derived products and oils—have been published in recent years demonstrating their effectiveness on xerosis and pruritus associated with a range of dermatoses, including atopic dermatitis [24,25,26], xerosis associated with chronic pruritus in elderly patients [27], mild-to-moderate plaque psoriasis [28], and foot xerosis [29]. Finally, in the first study of its kind to evaluate the effects of emollients on xerosis and pruritus in an African population, an 8-week regimen with a glycerol-based emollient was shown to lead to 80% reductions in xerosis severity in adults and children, and to 40% and 80% reductions in pruritus severity in adults and children, respectively [30]. However, around 41% of the patients in the study by Boralevi et al. [30] were also prescribed another topical treatment (most commonly a topical steroid) at inclusion. Comparison of the findings of these previous reports with those of the current study show that our study product was effective at reducing the severity of both xerosis and pruritus in patients with a range of dermatological diseases. It should also be noted that the majority of the previous studies assessed the effectiveness of emollients after several weeks of application, whereas the significant improvements in symptoms reported in our study were achieved after only a short 1-week period.
The largest improvement in VAS score for pruritus in our study was observed in patients that had persistent itch after successful scabies treatment. The prevalence of scabies worldwide is estimated to range from 0.2% to 71.4% of the population, with the highest disease burden being reported in tropical regions [31]. However, several reports indicate that there has been a sharp rise in the incidence of scabies over the past decade in several European countries, including Germany [32], Croatia [33], and Norway [34]. Itch may persist for 2–4 weeks after the end of successful scabies treatment and current European guidelines recommend repeated application of emollients to manage these symptoms [35]. Our results suggest that the study product may be useful for managing these short-term symptoms. However, as itch after successful scabies treatment may resolve naturally without treatment, these promising findings need to be evaluated further within the framework of a randomized controlled trial. It is also noteworthy that the emollient was also very effective against pruritic xerosis associated with prurigo nodularis of Hyde, a chronic skin condition characterized by intense pruritus. Prurigo nodularis of Hyde is very difficult to treat and, although emollients are recommended as base therapy to prevent xerosis, effective management usually involves the use of topical or interlesional steroids and systemic immunosuppressive drugs [36]. To our knowledge, no previous clinical studies—using a robust study design and validated assessment tools—have been published demonstrating the effectiveness of other emollients for the treatment of persistent itch in patients post scabies treatment and for the intense pruritus associated with prurigo nodularis of Hyde.
In addition to its effectiveness for improving pruritus and xerosis, our study also showed that the product was effective at reducing sleep disturbance and itch duration, and lessened the impact of the skin manifestations on patient QoL. Xerosis and pruritus are known to have a substantial impact on QoL [8], and to be associated with sleep deficiency in both adults and children [37, 38]. After 7 days of using the study product, the patients in our study reported significant improvements in sleep quality and DLQI scores, with skin symptoms having only a mild impact on the life of patients. This improvement in DLQI scores is of particular interest given that the results of previous studies did not always show improvement in clinical symptoms correlating to significant improvements in QoL scores [39, 40]. However, improvements in QoL after emollient use have been demonstrated in some studies, including that by Boralevi et al. [30] in adult African patients.
Emollients and creams are often used alongside systemic and topical pharmacologic treatments as adjunct therapies or maintenance interventions to prevent flare-ups and relapses [22, 24]. The majority of the patients included in our study were prescribed the study product without any concurrent medication and did not initiate a pharmacologic treatment during the course of the study (n = 3369, 57.0% of patients). However, use of a pharmacologic treatment could not be excluded or was reported at inclusion for 1991 patients (33.7%), and 550 patients were known to have started a new treatment during the study period (9.3%). Our post hoc analyses of the subpopulation of patients who used the study product alone clearly demonstrated that use of the study product as a monotherapy led to the significant improvements in xerosis and pruritus severity, together with the reduction in itch duration and the improvements in sleep quality and DLQI scores. On the other hand, large improvements in clinical symptoms were also observed in the subpopulation using the study product in combination with a pharmacologic therapy. Although further comparative trials would be required to confirm these findings, our results strongly indicate that the study product was also beneficial to patients when used as an adjunct treatment.
One of the strengths of our study was that its noninterventional nature allowed the effectiveness of the study product to be evaluated in a large cohort of patients in a real-life setting. Owing to the size of the cohort and the multicenter nature of the study—involving patients from European, South American, Asian, and North and South African populations—the level of generalizability of our findings can be considered to be very high. One of the major limitations of the real-world study was that its design did not allow us to demonstrate the effectiveness of our study product relative to that of a placebo; however, the before-and-after analysis of the population, combined with our subpopulation analyses of patients receiving the study product alone or in combination with additional treatments, clearly allowed us to demonstrate the effectiveness of our study product in patients with a wide range of dermatologic and systemic diseases.
Another limitation of our study was the short duration of the evaluation period, which did not allow us to evaluate whether the beneficial effects of the product were sustained after extended use. However, our findings clearly demonstrate the beneficial effects of using the study product after only 1 week. A recent study analyzing the kinetics of the response to regular emollient use in children with mild-to-moderate atopic dermatitis also found that the effects of emollients at reducing xerosis and improving SCORAD were already visible after 1 week, and that the improvements were progressive with regular emollient use over a 12-week period [41]. Further studies are required to determine if regular use of our study product over a longer period would result in further improvements in symptoms and if the symptom relief can be sustained. Finally, although all of the clinical assessment tools used in this study are widely used and validated instruments for assessing dermatological symptoms, with the exception of xerosis severity which was assessed by physicians, all other assessments, including the assessment of product use, were evaluated through questionnaires filled in by the patients themselves, introducing the potential for self-reporting bias.